A series of novel xerogels based on sodium acrylate (NaA), montmorillonite (MMT), and N,NЈ-methylene-bisacrylamide (NMBA) were prepared by inverse suspension polymerization and water solution polymerization. The influences of pure MMT, intercalated MMT, the method of polymerization, and the content of the MMT in the copolymeric gels on the water absorbency and the initial absorption rate in deionized water and various salt solutions were investigated. Results showed that the water absorbency was increased by adding a small amount of the pure MMT into the copolymeric gels, but decreased by adding intercalated MMT into the gels. In addition, the water absorbency of the gels prepared by water solution polymerization was lower than that prepared by inverse suspension polymerization

A series of xerogels based on sodium acrylate, nonionic monomers such as 2-hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol) methacrylate (PEGMA), and N,NЈ-methylene bisacrylamide were prepared by inverse suspension polymerization. The results indicate that the water absorbencies for these two gel series were effectively improved by the addition of a small amount of nonionic monomer (HEMA or PEGMA). The initial absorption rates in deionized water were faster for the PEGMA gels than for the HEMA gels. Scanning electron microscopy showed that the spherical particle size was smaller for the PEGMA gels than for the HEMA gels. In addition, the water absorbency of the gels in various salt solutions decreased with increasing ionic strength, especially for the multivalent salt solutions.

ABSTRACT:In a previous study, we prepared a series of xerogels based on sodium acrylate (NaA) and 2-hydroxyethyl methacrylate (HEMA, OE ϭ 1) or poly(ethylene glycol) methacrylate (PEGMA, OE ϭ 6) with different oxyethylene (OE) units. The effect of the contents of HEMA and PEGMA in the copolymeric gel on the swelling behavior in deionized water and various saline solutions was studied. Their results showed that the water absorbencies for these two series gels were effectively improved by adding a small amount of HEMA or PEGMA. In this article, a series of novel xerogels based on NaA and hydrophilic monomer poly(ethylene glycol) methyl ether acrylate (PEGMEA n ), which was synthesized from acryloyl chloride and poly(ethylene glycol) monomethyl ether with three oxyethylene (OE ϭ 9, 16, 45) chain lengths, were prepared by inverse suspension polymerization. The effects of OE chain length in the copolymeric gel on the water absorption behavior and initial absorption rate for the present xerogels were investigated. Results showed that adding a small amount of PEGMEA n could effectively increase the water absorbency of the gels. In addition, the water absorbency decreased with an increase of the OE chain length in PEGMEA n . The initial absorption rate for the present copolymeric gels increased with increasing OE chain length in PEGMEA n and the content of PEGMEA n in the copolymeric gels.